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MAMMALIAN RADIATION GENETICS 



females, were offspring of males exposed to 250-kvp x-rays at an inten- 

 sity of approximately 80 r per min and for doses of 500, 750, or 1000 r. 

 They were conceived within from 2 to 30 days after irradiation of the 

 father. Their fertihty was adequately tested, and the status of those 

 classified as semisteriles has been further checked in descendant genera- 

 tions. The results obtained are compared with those of Snell (15) and 

 Hertwig (8), for similar dose ranges, in Table 1. Averaging the effects 



TABLE 1 



Incidence of Sterility and Semisterility in Offspring (Male and 

 Female Combined) of Irradiated Males 



over wide dose ranges is, of course, a poor procedure, but over the ranges 

 given here is presumably justifiable for the purpose of a rough compari- 

 son; and, in any case, Snell does not tabulate his results in a way that 

 can be used to calculate the incidence for each dose. 



The high rate of induction of reciprocal translocations by radiation in 

 the mouse is, therefore, supported by three independent investigations 

 and is not refuted by the results of Lorenz et at. 



It is noteworthy that this rate is far higher than in the fruit fly. The 

 yield from an acute dose of about 600 r in the mouse is comparable to 

 that from 5000 r in Drosophila melanog aster. The difference between the 

 two species is presumably due to the larger number of chromosomes or 

 amount of chromatin in the mouse. It is, therefore, reasonable to guess 

 that the rate in man would be as high as that in the mouse or even 

 higher. If the hazard from this were not controllable, it would be seri- 

 ous. Fortunately, as has already been pointed out, Hertwig's work 



